The turncoat who defected to the Soviet Union had been living in Russia since he escaped from Wormwood Scrubs prison in 1966.
Blake was sentenced to a record 42-year jail sentence in London in 1961 for spilling British secrets, sending dozens of Western agents to their deaths.
He himself claimed to have betrayed up to 600 of his comrades to the Soviets during the Cold War.
The traitor went on the run after climbing over Wormwood Scrubs’ prison wall in 1966, soon after England won the World Cup.
In a dash across Europe, he then crossed into East Berlin and into the hands of his grateful Soviet spymasters.
“The bitter news has come – the legendary George Blake is gone,” Sergey Ivanov, spokesman for the SVR foreign intelligence agency, formerly the KGB, announced on Boxing Day.
“He died of old age, his heart stopped.”
Blake marked his 98th birthday last month with a message from spymaster Sergey Naryshkin who sent him Russia’s “warm and sincere wishes”.
At his death, he was the oldest KGB veteran.
Pals said while visually impaired in his latter years, he continued to “spy” on Britain by tuning into BBC radio.
I think that the word ‘traitor’ can be applied in describing me – but there are reasons which can justify what I’ve doneGeorge Blake
The spook had been holed up at his dacha – country house – near Moscow which was a gift from the KGB amid efforts to keep him safe from coronavirus.
“I think that the word ‘traitor’ can be applied in describing me – but there are reasons which can justify what I’ve done,” he once said.
Despite being a fugitive from justice in Britain since 1966, he kept in contact with the three sons who he deserted when he fled to Moscow.